1. Field of the Invention
The present invention relates to an expansible fastener adapted to be inserted in aligned holes in a plurality of panels for detachably securing them to each other with a force as large as would be provided by a screw.
2. Prior Art
Expansion type fasteners made of resinous materials for securing plural panels are disclosed in U.S. Pat. Nos. 3,112,547 and 3,918,130. Each of these known fasteners comprises an expansible fastener part having a leg and an expander part complementary to each other. After the leg of the fastener part has been positioned in aligned holes of panels, the expander part is pushed into the fastener part to spread the leg of the latter outward for thereby fastening the panels rigidly together.
The fastener shown in U.S. Pat. No. 3,112,547 includes a fastener part whose leg terminates at multiple fingers spaced apart from each other on its end which is to confront a panel surface. A drawback brought about here is that the split end of the leg is liable to get caught partly by a panel surface adjacent to a hole during insertion of the fastener part into the hole due to an irregular distribution of hole diameters or the like. The result is a poor operationability and this is particularly pronounced when diameters of holes in panels are relatively small. The fastener when removed from panels can not elastically regain its fully unstressed position so that reuse of the fastener is impossible without experiencing a far poorer operationability.
Two different types of expansible fasteners are proposed in U.S. Pat. No. 3,918,130. A first type of fastener has a leg of its fastener part made up of two independent complementary members which are shaped on their inner walls to interlock with an outer periphery of an expander part in a specific manner. After insertion of the fastener part in aligned holes in panels, the fastener part and expander part are secured to each other while fastening the panels together. The bisected fastener part, however, increases time and labor necessary for the assemblage of the fastener while interlocking of the fastener and expander parts is permitted only in a particular orientation alone. The expander part can not be inserted in the fastener part unless after positioning the latter in holes of panels, resulting in a farther fall of the operationability. A second type of fastener has a fastener part whose legs are separate at their upper ends but integral with each other at the lower ends. Such a configuration of fastener parts avoids the inconvenience discussed in connection with the fastener of U.S. Pat. No. 3,112,547. Nevertheless, the operationability is not fully acceptable because the bifurcated end of the fastener part does not permit the expander part to be coupled with the fastener part until after the insertion of the fastener part in holes in panels.